Tottenham missed the chance to move into the Premier League's top four as Southampton delivered a battling 1-1 draw for their under-pressure boss Mauricio Pellegrino.
Harry Kane scored his 99th league goal after Davinson Sanchez had given Southampton a surprise first-half lead by turning the ball into his own net.
Both sides had chances to nick a late winner but Spurs were the more frustrated at the final whistle, with fourth-placed Liverpool now able to pull five points clear with a win over Swansea on Monday.
For Southampton, who stay 18th, this was a morale-boosting point gained in the battle against relegation and in particular for their manager Pellegrino.
The grumbling at St Mary's has grown louder in recent weeks and with Marco Silva available after being sacked by Watford hours before kick-off here, the atmosphere could quickly have turned sour.
The south-coast side are without a win in 11 games, the longest drought of any team currently in the division, but a gutsy, aggressive display earned the players warm applause as they left the pitch.
It was five years this week that another Argentinian with no Premier League experience faced early scepticism on the south coast but, unlike Pellegrino, Pochettino was able to marry tactical change with short-term results.
Tottenham, however, painfully missed the creativity of Christian Eriksen, who was ill, while Hugo Lloris' virus gave Michel Vorm his first league start in goal since April last year.
Southampton made two changes as well. Mario Lemina and Manolo Gabbiadini came in -- Gabbiadini having scored in only two of his 25 games this season.
Vorm was tested twice early on, first holding a fizzing shot from Gabbiadini and then rushing out to claim after a promising Southampton break.
Saints were punishing Serge Aurier down Tottenham's right and it was from there they took a surprise lead as Ryan Bertrand's cross was turned into his own net by the sliding Sanchez.
The hosts' advantage lasted only three minutes, however, and it could have been fewer had Eric Dier's shot not crashed against the post. Moments later, Kane ghosted past Jack Stephens to nod home Ben Davies' corner.
Sissoko and Stephens both spurned chances when free in the box while Kane impressed when he pulled the ball out of the air and pushed it through Cedric's legs.
Tottenham were out early for the start of the second half but failed to shake off the loose touches and misplaced passes that continually stalled their attacks.
Erik Lamela replaced Son Heung-Min with 18 minutes left and Kieran Trippier came on for the injured Aurier - but there was little sign of either side breaking through until the final five minutes.
Lamela, teed up by Sissoko, saw a finish blocked by the flailing leg of Stephens before a glorious chance fell to Saints substitute Michael Obafemi. He had only Vorm to beat from eight yards but skewed wide.
Kane almost had the last word in stoppage time but his angled shot fired just wide of the far post and agonisingly out of reach of the leaping Lamela.